"""Global IPython app to support test running.

We must start our own ipython object and heavily muck with it so that all the
modifications IPython makes to system behavior don't send the doctest machinery
into a fit.  This code should be considered a gross hack, but it gets the job
done.
"""

from __future__ import absolute_import

#-----------------------------------------------------------------------------
# Module imports
#-----------------------------------------------------------------------------

# From the standard library
import __builtin__
import commands
import new
import os
import sys

from . import tools
from IPython.utils.genutils import Term

#-----------------------------------------------------------------------------
# Functions
#-----------------------------------------------------------------------------

# Hack to modify the %run command so we can sync the user's namespace with the
# test globals.  Once we move over to a clean magic system, this will be done
# with much less ugliness.

class py_file_finder(object):
    def __init__(self,test_filename):
        self.test_filename = test_filename
        
    def __call__(self,name):
        from IPython.utils.genutils import get_py_filename
        try:
            return get_py_filename(name)
        except IOError:
            test_dir = os.path.dirname(self.test_filename)
            new_path = os.path.join(test_dir,name)
            return get_py_filename(new_path)
    

def _run_ns_sync(self,arg_s,runner=None):
    """Modified version of %run that syncs testing namespaces.

    This is strictly needed for running doctests that call %run.
    """
    #print >> sys.stderr,  'in run_ns_sync', arg_s  # dbg
    
    _ip = get_ipython()
    finder = py_file_finder(arg_s)
    out = _ip.magic_run_ori(arg_s,runner,finder)
    return out


class ipnsdict(dict):
    """A special subclass of dict for use as an IPython namespace in doctests.

    This subclass adds a simple checkpointing capability so that when testing
    machinery clears it (we use it as the test execution context), it doesn't
    get completely destroyed.
    """
    
    def __init__(self,*a):
        dict.__init__(self,*a)
        self._savedict = {}
        
    def clear(self):
        dict.clear(self)
        self.update(self._savedict)

    def _checkpoint(self):
        self._savedict.clear()
        self._savedict.update(self)

    def update(self,other):
        self._checkpoint()
        dict.update(self,other)

        # If '_' is in the namespace, python won't set it when executing code,
        # and we have examples that test it.  So we ensure that the namespace
        # is always 'clean' of it before it's used for test code execution.
        self.pop('_',None)

        # The builtins namespace must *always* be the real __builtin__ module,
        # else weird stuff happens.  The main ipython code does have provisions
        # to ensure this after %run, but since in this class we do some
        # aggressive low-level cleaning of the execution namespace, we need to
        # correct for that ourselves, to ensure consitency with the 'real'
        # ipython.
        self['__builtins__'] = __builtin__
        

def get_ipython():
    # This will get replaced by the real thing once we start IPython below
    return start_ipython()

def start_ipython():
    """Start a global IPython shell, which we need for IPython-specific syntax.
    """
    global get_ipython

    # This function should only ever run once!
    if hasattr(start_ipython,'already_called'):
        return
    start_ipython.already_called = True

    # Ok,  first time we're called, go ahead
    from IPython.core import ipapp, iplib
    
    def xsys(cmd):
        """Execute a command and print its output.

        This is just a convenience function to replace the IPython system call
        with one that is more doctest-friendly.
        """
        cmd = _ip.var_expand(cmd,depth=1)
        sys.stdout.write(commands.getoutput(cmd))
        sys.stdout.flush()

    # Store certain global objects that IPython modifies
    _displayhook = sys.displayhook
    _excepthook = sys.excepthook
    _main = sys.modules.get('__main__')

    argv = tools.default_argv()
    
    # Start IPython instance.  We customize it to start with minimal frills.
    user_ns,global_ns = iplib.make_user_namespaces(ipnsdict(),{})
    ip = ipapp.IPythonApp(argv, user_ns=user_ns, user_global_ns=global_ns)
    ip.initialize()
    ip.shell.builtin_trap.set()
    # Set stderr to stdout so nose can doctest exceptions
    ## Term.cerr = sys.stdout
    ## sys.stderr = sys.stdout
    ip.shell.InteractiveTB.out_stream = 'stdout'
    # Butcher the logger
    ip.shell.log = lambda *a,**k: None
    
    # Deactivate the various python system hooks added by ipython for
    # interactive convenience so we don't confuse the doctest system
    sys.modules['__main__'] = _main
    sys.displayhook = _displayhook
    sys.excepthook = _excepthook

    # So that ipython magics and aliases can be doctested (they work by making
    # a call into a global _ip object).  Also make the top-level get_ipython
    # now return this without calling here again
    _ip = ip.shell
    get_ipython = _ip.get_ipython
    __builtin__._ip = _ip
    __builtin__.get_ipython = get_ipython

    # Modify the IPython system call with one that uses getoutput, so that we
    # can capture subcommands and print them to Python's stdout, otherwise the
    # doctest machinery would miss them.
    ip.shell.system = xsys

    # XXX - For some very bizarre reason, the loading of %history by default is
    # failing.  This needs to be fixed later, but for now at least this ensures
    # that tests that use %hist run to completion.
    from IPython.core import history
    history.init_ipython(ip.shell)
    if not hasattr(ip.shell,'magic_history'):
        raise RuntimeError("Can't load magics, aborting")

    return _ip